When switching off electrical currents in installation equipment, such as circuit breakers, a switching arc is formed when the contacts are opened. The arc heats up the air in the switching chamber, leading to a pressure increase and thus to the heated gases flowing out through exhaust openings—referred to as exhaustion in the following. These heated and conductive gases also contain highly dispersed solid particles and molten metal particles, and the conductivity of said gases also changes, depending on the composition and gas temperature, once they have left the installation equipment. When designing switching chambers (housing strength), the processes of exhaustion (temperature, chamber pressure) have to be taken into account.
With regard to the overall cross section of the through-openings, the dimensions of a switching gas cooling assembly are substantially determined by and dependent on the switching capacity or nominal current of the installation equipment. The dimensions are generally optimized such that a high cooling capacity is produced. This generally requires relatively narrow through-openings in the switching gas cooling assembly.
With regard to the prior art of switching gas cooling assemblies having narrow through-openings, the following apparatuses should therefore be mentioned by way of example:
A cooling apparatus in low-voltage circuit breakers is known, in which a close-meshed metal net or grating is used (EP 0817223 B1). Another embodiment is formed as a plate stack (DE 102012110409 A1).
Forming the through-openings as narrow through-openings is disadvantageous in that, after some time, the through-openings become clogged by particles carried along in the exhaust gases, damaging the switching gas cooling assembly. The flow cross section in the switching gas cooling assembly is reduced. The cooling action declines, which in turn affects the pressure and switching conditions in the switching chamber.